Qt文件下载工具

在Qt中实现文件下载功能，通常可以通过多种方式来完成，包罗使用 QNetworkAccessManager 和 QNetworkReply 类，或者使用更高级别的 QHttpMultiPart 类。以下是两种常见的实现方法：
方法1：使用 QNetworkAccessManager 和 QNetworkReply
创建 QNetworkAccessManager 对象：这个对象负责管理和处置惩罚网络哀求。
发送 GET 哀求：使用 QNetworkAccessManager 的 get 方法来发送一个GET哀求到指定的URL。
接收数据：通过重写槽函数 readyRead 来接收数据。
生存文件：将接收到的数据写入到文件中。
处置惩罚完成：当下载完成后，重写 finished 槽函数来处置惩罚完成的逻辑。

2. #ifndef DOWNLOAD_DIALOG_H
3. #define DOWNLOAD_DIALOG_H
5. #include <QDir>
6. #include <QDialog>
7. #include <ui_Downloader.h>
9. namespace Ui {
10. class Downloader;
11. }
13. class QNetworkReply;
14. class QNetworkAccessManager;
16. /**
17. * \brief Implements an integrated file downloader with a nice UI
18. */
19. class Downloader : public QWidget
20. {
21.     Q_OBJECT
23. signals:
24.     void downloadFinished (const QString& url, const QString& filepath);
26. public:
27.     explicit Downloader (QWidget* parent = 0);
28.     ~Downloader();
30.     bool useCustomInstallProcedures() const;
32.     QString downloadDir() const;
33.     void setDownloadDir(const QString& downloadDir);
35. public slots:
36.     void setUrlId (const QString& url);
37.     void startDownload (const QUrl& url);
38.     void setFileName (const QString& file);
39.     void setUserAgentString (const QString& agent);
40.     void setUseCustomInstallProcedures (const bool custom);
42. private slots:
43.     void finished();
44.     void openDownload();
45.     void installUpdate();
46.     void cancelDownload();
47.     void saveFile (qint64 received, qint64 total);
48.     void calculateSizes (qint64 received, qint64 total);
49.     void updateProgress (qint64 received, qint64 total);
50.     void calculateTimeRemaining (qint64 received, qint64 total);
52. private:
53.     qreal round (const qreal& input);
55. private:
56.     QString m_url;
57.     uint m_startTime;
58.     QDir m_downloadDir;
59.     QString m_fileName;
60.     Ui::Downloader* m_ui;
61.     QNetworkReply* m_reply;
62.     QString m_userAgentString;
63.     bool m_useCustomProcedures;
64.     QNetworkAccessManager* m_manager;
65. };
67. #endif

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1. #pragma execution_character_set("utf-8")
2. #include <QDir>
3. #include <QFile>
4. #include <QProcess>
5. #include <QMessageBox>
6. #include <QNetworkReply>
7. #include <QDesktopServices>
8. #include <QNetworkAccessManager>
10. #include <math.h>
12. #include "Downloader.h"
14. static const QString PARTIAL_DOWN (".part");
16. Downloader::Downloader (QWidget* parent) : QWidget (parent)
17. {
18.     m_ui = new Ui::Downloader;
19.     m_ui->setupUi (this);
20.     /* Initialize private members */
21.     m_manager = new QNetworkAccessManager();
23.     /* Initialize internal values */
24.     m_url = "";
25.     m_fileName = "";
26.     m_startTime = 0;
27.     m_useCustomProcedures = false;
29.     /* Set download directory */
30.     m_downloadDir = QDir::homePath() + "/Downloads/";
31.     /* Configure the appearance and behavior of the buttons */
32.     m_ui->openButton->setEnabled (false);
33.     m_ui->openButton->setVisible (false);
34.     connect (m_ui->stopButton, SIGNAL (clicked()),
35.              this,               SLOT (cancelDownload()));
36.     connect (m_ui->openButton, SIGNAL (clicked()),
37.              this,               SLOT (installUpdate()));
39.     /* Resize to fit */
40. }
42. Downloader::~Downloader()
43. {
44.     delete m_ui;
45.     delete m_reply;
46.     delete m_manager;
47. }
49. /**
50. * Returns \c true if the updater shall not intervene when the download has
51. * finished (you can use the \c QSimpleUpdater signals to know when the
52. * download is completed).
53. */
54. bool Downloader::useCustomInstallProcedures() const
55. {
56.     return m_useCustomProcedures;
57. }
59. /**
60. * Changes the URL, which is used to indentify the downloader dialog
61. * with an \c Updater instance
62. *
63. * \note the \a url parameter is not the download URL, it is the URL of
64. *       the AppCast file
65. */
66. void Downloader::setUrlId (const QString& url)
67. {
68.     m_url = url;
69. }
71. /**
72. * Begins downloading the file at the given \a url
73. */
74. void Downloader::startDownload (const QUrl& url)
75. {
76.     /* Reset UI */
77.     m_ui->progressBar->setValue (0);
78.     m_ui->stopButton->setText (tr ("Stop"));
79.     m_ui->downloadLabel->setText (tr ("Downloading updates"));
80.     m_ui->timeLabel->setText (tr ("Time remaining") + ": " + tr ("unknown"));
82.     /* Configure the network request */
83.     QNetworkRequest request (url);
84.     if (!m_userAgentString.isEmpty())
85.         request.setRawHeader ("User-Agent", m_userAgentString.toUtf8());
87.     /* Start download */
88.     m_reply = m_manager->get (request);
89.     m_startTime = QDateTime::currentDateTime().toTime_t();
91.     /* Ensure that downloads directory exists */
92.     if (!m_downloadDir.exists())
93.         m_downloadDir.mkpath (".");
95.     /* Remove old downloads */
96.     QFile::remove (m_downloadDir.filePath (m_fileName));
97.     QFile::remove (m_downloadDir.filePath (m_fileName + PARTIAL_DOWN));
99.     /* Update UI when download progress changes or download finishes */
100.     connect (m_reply, SIGNAL (downloadProgress (qint64, qint64)),
101.              this,      SLOT (updateProgress   (qint64, qint64)));
102.     connect (m_reply, SIGNAL (finished ()),
103.              this,      SLOT (finished ()));
104.     connect (m_reply, SIGNAL (redirected       (QUrl)),
105.              this,      SLOT (startDownload    (QUrl)));
107. }
109. /**
110. * Changes the name of the downloaded file
111. */
112. void Downloader::setFileName (const QString& file)
113. {
114.     m_fileName = file;
116.     if (m_fileName.isEmpty())
117.         m_fileName = "QSU_Update.bin";
118. }
120. /**
121. * Changes the user-agent string used to communicate with the remote HTTP server
122. */
123. void Downloader::setUserAgentString (const QString& agent)
124. {
125.     m_userAgentString = agent;
126. }
128. void Downloader::finished()
129. {
130.     /* Rename file */
131.     QFile::rename (m_downloadDir.filePath (m_fileName + PARTIAL_DOWN),
132.                    m_downloadDir.filePath (m_fileName));
134.     /* Notify application */
135.     emit downloadFinished (m_url, m_downloadDir.filePath (m_fileName));
137.     /* Install the update */
138.     m_reply->close();
139.     installUpdate();
140.     setVisible (false);
141. }
143. /**
144. * Opens the downloaded file.
145. * \note If the downloaded file is not found, then the function will alert the
146. *       user about the error.
147. */
148. void Downloader::openDownload()
149. {
150.     if (!m_fileName.isEmpty())
151.         QDesktopServices::openUrl (QUrl::fromLocalFile (m_downloadDir.filePath (
152.                                                             m_fileName)));
154.     else {
155.         QMessageBox::critical (this,
156.                                tr ("Error"),
157.                                tr ("Cannot find downloaded update!"),
158.                                QMessageBox::Close);
159.     }
160. }
162. /**
163. * Instructs the OS to open the downloaded file.
164. *
165. * \note If \c useCustomInstallProcedures() returns \c true, the function will
166. *       not instruct the OS to open the downloaded file. You can use the
167. *       signals fired by the \c QSimpleUpdater to install the update with your
168. *       own implementations/code.
169. */
170. void Downloader::installUpdate()
171. {
172.     if (useCustomInstallProcedures())
173.         return;
175.     /* Update labels */
176.     m_ui->stopButton->setText    (tr ("Close"));
177.     m_ui->downloadLabel->setText (tr ("Download complete!"));
178.     m_ui->timeLabel->setText     (tr ("The installer will open separately")
179.                                   + "...");
181.     /* Ask the user to install the download */
182.     QMessageBox box;
183.     box.setIcon (QMessageBox::Question);
184.     box.setDefaultButton   (QMessageBox::Ok);
185.     box.setStandardButtons (QMessageBox::Ok | QMessageBox::Cancel);
186.     box.setInformativeText (tr ("Click "OK" to begin installing the update"));
187.     box.setText ("<h3>" +
188.                  tr ("In order to install the update, you may need to "
189.                      "quit the application.")
190.                  + "</h3>");
192.     /* User wants to install the download */
193.     if (box.exec() == QMessageBox::Ok) {
194.         if (!useCustomInstallProcedures())
195.             openDownload();
196.     }
198.     /* Wait */
199.     else {
200.         m_ui->openButton->setEnabled (true);
201.         m_ui->openButton->setVisible (true);
202.         m_ui->timeLabel->setText (tr ("Click the "Open" button to "
203.                                       "apply the update"));
204.     }
205. }
207. /**
208. * Prompts the user if he/she wants to cancel the download and cancels the
209. * download if the user agrees to do that.
210. */
211. void Downloader::cancelDownload()
212. {
213.     if (!m_reply->isFinished()) {
214.         QMessageBox box;
215.         box.setWindowTitle (tr ("Updater"));
216.         box.setIcon (QMessageBox::Question);
217.         box.setStandardButtons (QMessageBox::Yes | QMessageBox::No);
218.         box.setText (tr ("Are you sure you want to cancel the download?"));
220.         if (box.exec() == QMessageBox::Yes) {
221.             m_reply->abort();
222.         }
223.     }
224. }
226. /**
227. * Writes the downloaded data to the disk
228. */
229. void Downloader::saveFile (qint64 received, qint64 total)
230. {
231.     Q_UNUSED(received);
232.     Q_UNUSED(total);
234.     /* Check if we need to redirect */
235.     QUrl url = m_reply->attribute (
236.                 QNetworkRequest::RedirectionTargetAttribute).toUrl();
237.     if (!url.isEmpty()) {
238.         startDownload (url);
239.         return;
240.     }
242.     /* Save downloaded data to disk */
243.     QFile file (m_downloadDir.filePath (m_fileName + PARTIAL_DOWN));
244.     if (file.open (QIODevice::WriteOnly | QIODevice::Append)) {
245.         file.write (m_reply->readAll());
246.         file.close();
247.     }
248. }
251. /**
252. * Calculates the appropiate size units (bytes, KB or MB) for the received
253. * data and the total download size. Then, this function proceeds to update the
254. * dialog controls/UI.
255. */
256. void Downloader::calculateSizes (qint64 received, qint64 total)
257. {
258.     QString totalSize;
259.     QString receivedSize;
261.     if (total < 1024)
262.         totalSize = tr ("%1 bytes").arg (total);
264.     else if (total < 1048576)
265.         totalSize = tr ("%1 KB").arg (round (total / 1024));
267.     else
268.         totalSize = tr ("%1 MB").arg (round (total / 1048576));
270.     if (received < 1024)
271.         receivedSize = tr ("%1 bytes").arg (received);
273.     else if (received < 1048576)
274.         receivedSize = tr ("%1 KB").arg (received / 1024);
276.     else
277.         receivedSize = tr ("%1 MB").arg (received / 1048576);
279.     m_ui->downloadLabel->setText (tr ("Downloading updates")
280.                                   + " (" + receivedSize + " " + tr ("of")
281.                                   + " " + totalSize + ")");
282. }
284. /**
285. * Uses the \a received and \a total parameters to get the download progress
286. * and update the progressbar value on the dialog.
287. */
288. void Downloader::updateProgress (qint64 received, qint64 total)
289. {
290.     if (total > 0) {
291.         m_ui->progressBar->setMinimum (0);
292.         m_ui->progressBar->setMaximum (100);
293.         m_ui->progressBar->setValue ((received * 100) / total);
295.         calculateSizes (received, total);
296.         calculateTimeRemaining (received, total);
297.         saveFile (received, total);
298.     }
300.     else {
301.         m_ui->progressBar->setMinimum (0);
302.         m_ui->progressBar->setMaximum (0);
303.         m_ui->progressBar->setValue (-1);
304.         m_ui->downloadLabel->setText (tr ("Downloading Updates") + "...");
305.         m_ui->timeLabel->setText (QString ("%1: %2")
306.                                   .arg (tr ("Time Remaining"))
307.                                   .arg (tr ("Unknown")));
308.     }
309. }
311. /**
312. * Uses two time samples (from the current time and a previous sample) to
313. * calculate how many bytes have been downloaded.
314. *
315. * Then, this function proceeds to calculate the appropiate units of time
316. * (hours, minutes or seconds) and constructs a user-friendly string, which
317. * is displayed in the dialog.
318. */
319. void Downloader::calculateTimeRemaining (qint64 received, qint64 total)
320. {
321.     uint difference = QDateTime::currentDateTime().toTime_t() - m_startTime;
323.     if (difference > 0) {
324.         QString timeString;
325.         qreal timeRemaining = total / (received / difference);
327.         if (timeRemaining > 7200) {
328.             timeRemaining /= 3600;
329.             int hours = int (timeRemaining + 0.5);
331.             if (hours > 1)
332.                 timeString = tr ("about %1 hours").arg (hours);
333.             else
334.                 timeString = tr ("about one hour");
335.         }
337.         else if (timeRemaining > 60) {
338.             timeRemaining /= 60;
339.             int minutes = int (timeRemaining + 0.5);
341.             if (minutes > 1)
342.                 timeString = tr ("%1 minutes").arg (minutes);
343.             else
344.                 timeString = tr ("1 minute");
345.         }
347.         else if (timeRemaining <= 60) {
348.             int seconds = int (timeRemaining + 0.5);
350.             if (seconds > 1)
351.                 timeString = tr ("%1 seconds").arg (seconds);
352.             else
353.                 timeString = tr ("1 second");
354.         }
356.         m_ui->timeLabel->setText (tr ("Time remaining") + ": " + timeString);
357.     }
358. }
360. /**
361. * Rounds the given \a input to two decimal places
362. */
363. qreal Downloader::round (const qreal& input)
364. {
365.     return roundf (input * 100) / 100;
366. }
368. QString Downloader::downloadDir() const
369. {
370.     return m_downloadDir.absolutePath();
371. }
373. void Downloader::setDownloadDir(const QString& downloadDir)
374. {
375.     if(m_downloadDir.absolutePath() != downloadDir) {
376.         m_downloadDir = downloadDir;
377.     }
378. }
380. /**
381. * If the \a custom parameter is set to \c true, then the \c Downloader will not
382. * attempt to open the downloaded file.
383. *
384. * Use the signals fired by the \c QSimpleUpdater to implement your own install
385. * procedures.
386. */
387. void Downloader::setUseCustomInstallProcedures (const bool custom)
388. {
389.     m_useCustomProcedures = custom;
390. }

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